The present invention relates generally to torsion damping assemblies comprising at least two coaxial parts mounted for relative angular displacement within a predetermined range against the action of chordally oriented resilient means circumferentially acting between the coaxial parts.
The present invention relates more particularly to such torsion damping assemblies comprising one coaxial part defined by a flange called a hub flange and the other coaxial part defined by two annular guide members disposed on the respective sides of the hub flange and spaced axially therefrom. The annular guide members are connected to each other by connecting members arranged parallel to the axis of the torsion damping assembly. The associated resilient means are partly accommodated in openings or windows formed in the hub flange and partly accommodated in openings or windows formed in the annular guide members.
In practice each of the connecting members for securing the annular guide members to each other comprises at each of its ends a neck portion or reduced section, axially beyond a shoulder. The neck portions extend through holes provided in the corresponding annular guide members. The free ends of the neck portions are suitably deformed, like a rivet, by swaging into contact with the corresponding guide members. Thus the connecting members are in effect rigidly fixed in the holes in the annular guide members.
Such a torsion damping assembly may be part of a clutch disc, in which case it is known as a damping hub, for use in automotive friction clutches.
In such a case one of the coaxial parts which is the driving part carries a friction disc having, on both sides along its outer periphery, friction facings by which the friction disc is adapted to be clamped or pressed between two plates fixed for rotation with a first shaft, which in practice is the driving shaft, and the crankshaft in the case of a motor vehicle, and the other coaxial part which is the output or driven part is carried by a hub which is splined for rotation on a second shaft which in practice is the driven shaft and the transmission input shaft in the case of a motor vehicle.
In practice, the connecting members carry all or part of the rotational torque transmitted from the driving shaft to the driven shaft in such a clutch disc.
In the case where the annular guide members are part of the driven part the friction disc is fixed to one of the annular guide members and the input torque is applied to only this annular guide member whereas the output torque is carried by both of the annular guide members.
Consequently, in the course of operation, each connecting member is not only subjected to the shearing force through their neck portions extending through the annular guide member but also an overturning moment with respect to the annular guide members since the transmission of the torque through the guide members is effected differentially. Such an overturning moment, which tends to unseat the neck portions of the connecting members from the holes in the annular guide members in which they are accommodated, may be detrimental to their mechanical securement and therefore to the ultimate service life of the clutch disc, particularly when the torque transmission is high.